The present invention is directed generally to a method and system for controlling the brake system of a tractor and trailer vehicle combination.
DE 101 28 692 A1 describes a method of the general type under consideration used to prevent a vehicle train comprising a tractor vehicle and a trailer vehicle (referred to therein as a “load train”) from overturning or rolling over while negotiating a curve. For this purpose, the vehicle train is braked by automatic actuation of the brake system when a specified, relatively high lateral acceleration is reached—the tractor vehicle and trailer vehicle each being braked. If the vehicle train is traveling on a driving roadway with relatively low coefficient of friction, wheel lock can occur, potentially leading to an undesired reduction of the cornering force of the wheels and, in turn, to swerving of the vehicle train. If the vehicle train is equipped with an anti-lock brake system (ABS), the wheel-lock protection function of the ABS prevents wheel lock and thus maintains the cornering force.
Commonly, a tractor vehicle equipped with an ABS is coupled with a trailer vehicle that lacks an ABS. In such case, wheel lock can occur during automatic braking of the trailer vehicle, potentially leading to an unsafe driving condition. In the method described in DE 101 28 692 A1, the brake system of the trailer vehicle is generally actuated intermittently in order to avoid such potentially unsafe driving conditions. However, this method makes no allowance for the real external conditions, such as the coefficient of friction of the driving roadway at that particular time. As a result, the physically possible braking effect of the trailer vehicle is not fully realized, especially on a driving roadway with relatively high coefficient of friction, and the measures to prevent the vehicle train from overturning cannot be applied optimally.
It is desired to provide an improved method and system for controlling the brake system of a vehicle train in which the conditions of the driving roadway are taken into account in braking of the trailer vehicle.